I am personally skeptical of the role of omega-3 and omega-6 in dementia, at least, one should never take these as supplements. It is a medical fact that they are highly unstable and basically worthless after only a day or so on the shelf, if not harmful.
One should only look to studies of genetically identical populations (you should be able to find one about nigerians in america) that acquire dementia at a high rate to observe that something about our capitalistically engineered environments is principally to blame.
But it might be more than just the carbohydrates and also name Balance of omega-3 and omega six.
https://alzheimer.ca/en/about-dementia/how-can-i-prevent-dem....